The field of the present disclosure relates generally to composite joints and, more specifically, to non-destructive bond strength verification techniques for composite joints.
At least some known aircraft components may be fabricated from multi-layer laminate structures of non-metallic composite materials such as carbon-fiber-reinforced polymer (CFRP). Composite materials generally have a high strength-to-weight ratio and may be formed in a variety of shapes and sizes. To reduce the weight of an aircraft, the composite materials may be used in combination with metallic materials, such as aluminum, titanium, and/or steel. Reducing overall weight generally contributes to increasing the fuel efficiency of the aircraft.
At least some known aircraft components fabricated from composite materials may be bonded together with an adhesive material. While the adhesive material is generally effective at bonding the components together, disbonding may occur during the service life of the aircraft. For example, disbonding may occur after prolonged use of the aircraft and/or may be caused when a foreign object impacts the materials during flight. Such disbonding may be difficult to detect during scheduled maintenance, and may be difficult to detect via visual inspection.
Moreover, it may be difficult and costly to verify that a successful bond between the components has been formed during manufacture of a part. For example, at least one known method of verifying bond strength includes forming process verification coupons using the same process under the same conditions as the part being formed. The strength of the process verification coupons is then evaluated via destructive testing, and the part is certified for service if the bond strength of the coupons is greater than a predetermined threshold. However, forming and evaluating process verification coupons is a time-consuming and laborious task, which provides only indirect bond strength verification of the bond formed between the components.